A man has admitted holding a pistol to his victim's head as he took $450 out of his pocket.

Sapati Junior Toleafoa, 23, pleaded guilty in the Christchurch District Court today to the charge of armed robbery.

Police said Toleafoa and a co-offender arrived at the victim's address on September 11 last year and found him on his driveway.

The co-offender told the victim he owed him money, and Toleafoa showed the man a concealed black pistol.

Toleafoa told the victim that he owed him money too, and that Toleafoa would come to his address every week and get money from him. He then pointed the barrel of the pistol at the victim's forehead and removed the cash from his pocket.

Both men struck the victim on the head, causing him to fall to the ground. Toleafoa lifted the victim off the ground and punched him in the face, saying he would return in a couple of weeks.

Judge Jane Farish remanded Toleafoa in custody to September 17 for sentencing, ordered a pre-sentence report, and read him the first of the three-strike warnings for violent offenders.